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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Estudo comparativo de duas técnicas laboratoriais para a detecção do HLA-B27 em pacientes portadores de espondiloartrite axial

Angeli, Ricardo dos Santos January 2017 (has links)
Introdução: A Espondiloartrite axial (EpA-ax) é uma doença inflamatória e crônica do grupo das Espondiloartrites (EpA). Ela acomete o sistema músculo esquelético ocasionando inflamação das articulações axiais (especialmente da sacroilíaca). Quando essas manifestações são evidenciadas por exames de imagem, temos a caracterização da Espondilite Anquilosante (EA). Do contrário, chamamos de EpA-axial não radiográfica (EpA-ax-nr). A Espondilite Anquilosante (EA) se caracteriza pelo envolvimento inflamatório de articulações do esqueleto axial e apendicular. Seu diagnóstico é baseado em achados clínicos e radiológicos, além da elevação de marcadores inflamatórios e presença do HLA-B27. Várias são as metodologias que se propõem a identificar o HLA-B27 e a Polymerase Chain Reaction (PCR) é tida como referência. Sua ampla utilização esbarra, no entanto, em questões que levam em conta o custo, oferta do exame e o tempo até a obtenção do resultado. Neste contexto, a Citometria de Fluxo (CF) surge como uma alternativa capaz de ajudar o médico na identificação deste marcador genético que pode ser importante para o diagnóstico e prognóstico dessa doença. Objetivo: Avaliar a correlação entre as técnicas laboratoriais mais utilizadas na prática clínica (CF e PCR), comparando sensibilidade e especificidade para detecção do HLA-B27 em pacientes com diagnóstico estabelecido de EpA-ax. Métodos: Estudo transversal, comparativo, com pacientes maiores de 18 anos de idade selecionados por conveniência, coletados ao longo de 2015, com diagnóstico estabelecido de EpA-ax, segundo os do grupo internacional ASAS (working group - Assessment of SpondyloArthritis Intenational Society). Para a análise estatística o coeficiente Kappa (P<0,005 foi adotado como parâmetro. Para a análise estatística o coeficiente Kappa (P<0,005 foi adotado como parâmetro. O teste Exato de Fisher foi utilizado para comparar as variáveis categóricas, o teste t de Student, para variáveis quantitativas com distribuição simétrica de amostras independentes. E as variáveis com distribuição assimétrica foram comparadas pelo teste de Mann-Whitney. Resultados: O coeficiente Kappa obtido para a determinação da concordância entre os testes foi de 0,454. Foram incluídos no estudo 62 pacientes, desses, sessenta preencheram os critérios para diagnóstico de EA e 2 para EpA-ax não radiográfica (EpA-ax-nr), 64,5% dos pacientes eram do sexo masculino, 88,7% se autodeclararam brancos, a idade média (± desvio padrão) foi de 54,5±12 anos e o tempo mediano (percentis 25 e 75) de diagnóstico de 14 (9 e 24) anos. Dentre as características clínicas apresentadas pela população estudada houve diferença estatisticamente significativa para a artrite periférica, sendo mais frequente no grupo HLA-B27 negativo que no grupo HLA-B27 positivo (P=0,032). Na análise de correlação, 90,3% apresentaram tipagem HLA-B27 positiva por CF e 79,0% pela técnica de PCR. Tendo o PCR como padrão ouro, a CF apresentou uma sensibilidade de 98,0%, especificidade de 38,5% e uma acurácia de 85,5%. Conclusão: Apesar da baixa especificidade apresentada pela CF, nosso estudo demonstrou que a CF tem alta sensibilidade e boa acurácia o que a torna uma boa alternativa para ser utilizada como um teste de triagem na busca da caracterização da doença. Apesar da moderada concordância com a técnica de referência, a CF poderia ajudar o médico a excluir resultados falsamente negativos, racionalizando assim a investigação laboratorial para o diagnóstico da EA. / Introduction: Axial spondyloarthritis (SpA-ax) is an inflammatory and chronic disease of the Spondyloarthritis (SpA) group. It affects the skeletal muscle system causing inflammation of the axial joints (especially of the sacroiliac). When these manifestations are evidenced by imaging tests, a characterization of Ankylosing Spondylitis (AS). Otherwise, we call the non-radiographic SpA-axial (SpA-ax-nr). AS marked by the inflammatory involvement of the axial and appendicular skeletal joints. The diagnosis is based on clinical and radiological findings, as well as the on the elevation of inflammatory markers and presence of HLA-B27. There are several methodologies to identify the HLA-B27 gene and a Polymerase Chain Reaction (PCR) is considered the reference method. However, its use on a large scale does not progress because it takes into account the cost, offer of the exam and the running time to obtain the result. In this context, Flow Cytometry (FC) emerges as an alternative method, helping with the physician in the determination of this genetic marker, important for the diagnosis and prognosis of disease. Objective: To evaluate the correlation between FC and PCR, comparing sensitivity and specificity for detection of HLA-B27 in patients with established diagnosis of SpA-ax. Methods: A cross sectional study including 62 patients recruited during 2015 month was conducted in Hospital de Clínicas de Porto Alegre, an university public hospital. The sample, recruited by convenience in the SpA clinic, was composed of patients ≥ 18 years old, fulfilling the Assessment of Spondyloarthritis (ASAS) criteria SpA-ax. All participants underwent HLA-B27 typing through FC and PCR. The kappa statistic was used to calculate the concordance between the FC and PCR. Taking PCR as the gold standard, sensitivity and specificity of FC to detect HLA-B27 were calculated. Results: The Kappa coefficient obtained to determine the agreement between the tests was 0.454. Sixty two patients were included in the study, sixty met the criteria for diagnosis of AS and two for SpA-ax-nr, 64.5% of the patients were male, 88.7% were self-declared mean age (± standard deviation) was 54.5 ± 12 years and median time (25th and 75th percentiles) for diagnosis was 14 (9 and 24) years. Among the clinical characteristics presented by the population studied, there was a statistically significant difference for peripheral arthritis, wich was more frequent in the HLA-B27 negative group than in the HLA-B27 positive group (P = 0.032). In the correlation analysis, 90.3% presented HLA-B27 positive typing by FC and 79.0% by PCR technique. When PCR was considered the gold standard, CF had a sensitivity of 98.0%, specificity of 38.5% and an accuracy of 85.5%. Conclusion: Despite the low specificity presented by FC, our study demonstrated that FC has high sensitivity and good accuracy, which makes it a good alternative to be used as a screening test in the search for the characterization of the disease. Despite the moderate agreement with the reference technique, FC could help the physician to exclude falsely negative results, thus rationalizing laboratory investigation for the diagnosis of AS.
192

Estudo comparativo de duas técnicas laboratoriais para a detecção do HLA-B27 em pacientes portadores de espondiloartrite axial

Angeli, Ricardo dos Santos January 2017 (has links)
Introdução: A Espondiloartrite axial (EpA-ax) é uma doença inflamatória e crônica do grupo das Espondiloartrites (EpA). Ela acomete o sistema músculo esquelético ocasionando inflamação das articulações axiais (especialmente da sacroilíaca). Quando essas manifestações são evidenciadas por exames de imagem, temos a caracterização da Espondilite Anquilosante (EA). Do contrário, chamamos de EpA-axial não radiográfica (EpA-ax-nr). A Espondilite Anquilosante (EA) se caracteriza pelo envolvimento inflamatório de articulações do esqueleto axial e apendicular. Seu diagnóstico é baseado em achados clínicos e radiológicos, além da elevação de marcadores inflamatórios e presença do HLA-B27. Várias são as metodologias que se propõem a identificar o HLA-B27 e a Polymerase Chain Reaction (PCR) é tida como referência. Sua ampla utilização esbarra, no entanto, em questões que levam em conta o custo, oferta do exame e o tempo até a obtenção do resultado. Neste contexto, a Citometria de Fluxo (CF) surge como uma alternativa capaz de ajudar o médico na identificação deste marcador genético que pode ser importante para o diagnóstico e prognóstico dessa doença. Objetivo: Avaliar a correlação entre as técnicas laboratoriais mais utilizadas na prática clínica (CF e PCR), comparando sensibilidade e especificidade para detecção do HLA-B27 em pacientes com diagnóstico estabelecido de EpA-ax. Métodos: Estudo transversal, comparativo, com pacientes maiores de 18 anos de idade selecionados por conveniência, coletados ao longo de 2015, com diagnóstico estabelecido de EpA-ax, segundo os do grupo internacional ASAS (working group - Assessment of SpondyloArthritis Intenational Society). Para a análise estatística o coeficiente Kappa (P<0,005 foi adotado como parâmetro. Para a análise estatística o coeficiente Kappa (P<0,005 foi adotado como parâmetro. O teste Exato de Fisher foi utilizado para comparar as variáveis categóricas, o teste t de Student, para variáveis quantitativas com distribuição simétrica de amostras independentes. E as variáveis com distribuição assimétrica foram comparadas pelo teste de Mann-Whitney. Resultados: O coeficiente Kappa obtido para a determinação da concordância entre os testes foi de 0,454. Foram incluídos no estudo 62 pacientes, desses, sessenta preencheram os critérios para diagnóstico de EA e 2 para EpA-ax não radiográfica (EpA-ax-nr), 64,5% dos pacientes eram do sexo masculino, 88,7% se autodeclararam brancos, a idade média (± desvio padrão) foi de 54,5±12 anos e o tempo mediano (percentis 25 e 75) de diagnóstico de 14 (9 e 24) anos. Dentre as características clínicas apresentadas pela população estudada houve diferença estatisticamente significativa para a artrite periférica, sendo mais frequente no grupo HLA-B27 negativo que no grupo HLA-B27 positivo (P=0,032). Na análise de correlação, 90,3% apresentaram tipagem HLA-B27 positiva por CF e 79,0% pela técnica de PCR. Tendo o PCR como padrão ouro, a CF apresentou uma sensibilidade de 98,0%, especificidade de 38,5% e uma acurácia de 85,5%. Conclusão: Apesar da baixa especificidade apresentada pela CF, nosso estudo demonstrou que a CF tem alta sensibilidade e boa acurácia o que a torna uma boa alternativa para ser utilizada como um teste de triagem na busca da caracterização da doença. Apesar da moderada concordância com a técnica de referência, a CF poderia ajudar o médico a excluir resultados falsamente negativos, racionalizando assim a investigação laboratorial para o diagnóstico da EA. / Introduction: Axial spondyloarthritis (SpA-ax) is an inflammatory and chronic disease of the Spondyloarthritis (SpA) group. It affects the skeletal muscle system causing inflammation of the axial joints (especially of the sacroiliac). When these manifestations are evidenced by imaging tests, a characterization of Ankylosing Spondylitis (AS). Otherwise, we call the non-radiographic SpA-axial (SpA-ax-nr). AS marked by the inflammatory involvement of the axial and appendicular skeletal joints. The diagnosis is based on clinical and radiological findings, as well as the on the elevation of inflammatory markers and presence of HLA-B27. There are several methodologies to identify the HLA-B27 gene and a Polymerase Chain Reaction (PCR) is considered the reference method. However, its use on a large scale does not progress because it takes into account the cost, offer of the exam and the running time to obtain the result. In this context, Flow Cytometry (FC) emerges as an alternative method, helping with the physician in the determination of this genetic marker, important for the diagnosis and prognosis of disease. Objective: To evaluate the correlation between FC and PCR, comparing sensitivity and specificity for detection of HLA-B27 in patients with established diagnosis of SpA-ax. Methods: A cross sectional study including 62 patients recruited during 2015 month was conducted in Hospital de Clínicas de Porto Alegre, an university public hospital. The sample, recruited by convenience in the SpA clinic, was composed of patients ≥ 18 years old, fulfilling the Assessment of Spondyloarthritis (ASAS) criteria SpA-ax. All participants underwent HLA-B27 typing through FC and PCR. The kappa statistic was used to calculate the concordance between the FC and PCR. Taking PCR as the gold standard, sensitivity and specificity of FC to detect HLA-B27 were calculated. Results: The Kappa coefficient obtained to determine the agreement between the tests was 0.454. Sixty two patients were included in the study, sixty met the criteria for diagnosis of AS and two for SpA-ax-nr, 64.5% of the patients were male, 88.7% were self-declared mean age (± standard deviation) was 54.5 ± 12 years and median time (25th and 75th percentiles) for diagnosis was 14 (9 and 24) years. Among the clinical characteristics presented by the population studied, there was a statistically significant difference for peripheral arthritis, wich was more frequent in the HLA-B27 negative group than in the HLA-B27 positive group (P = 0.032). In the correlation analysis, 90.3% presented HLA-B27 positive typing by FC and 79.0% by PCR technique. When PCR was considered the gold standard, CF had a sensitivity of 98.0%, specificity of 38.5% and an accuracy of 85.5%. Conclusion: Despite the low specificity presented by FC, our study demonstrated that FC has high sensitivity and good accuracy, which makes it a good alternative to be used as a screening test in the search for the characterization of the disease. Despite the moderate agreement with the reference technique, FC could help the physician to exclude falsely negative results, thus rationalizing laboratory investigation for the diagnosis of AS.
193

Polimorfismo Alélico do receptor FcyRIIA na Leishmaniose Tegumentar Americana / Allelic polymorphism in the receptor FcyRIIA Cutaneous Leishmaniasis

OLIVEIRA, Cristina Rodrigues de 13 February 2007 (has links)
Made available in DSpace on 2014-07-29T15:30:34Z (GMT). No. of bitstreams: 1 CRISTINA RODRIGUES DE OLIVEIRA.pdf: 2212867 bytes, checksum: a424437b0d0a13929b5f608708fec44a (MD5) Previous issue date: 2007-02-13 / The Fc&#947;RIIA, receptor for the Fc portion of IgG, expressed by macrophages, neutrophils, platelets and dendritic cells, bind to the subclasses of IgG with variable affinity, that can be influenced by the polymorphism in the gene that encodes this receptor. The substitution of the amino acid arginine (R) for histidine (H), in the 131 position, defines three allelic patterns, the homozygote H/H, R/R and the heterozygote H/R, conferring to the Fc&#947;RIIA H/H131 a greater affinity to the IgG2 and IgG3 subclasses. This can result in different responses to diverse pathogens. Studies show the importance of Fc&#947; receptors on the macrophage infection by amastigote forms of Leishmania sp, in addition to those for the complement (CR3) and for mannose (MR). Besides that, genetic factors related to the hosts are involved in the immune response to the leishmaniasis, among them, the Fc&#947;Rs. Until this time, we haven t found studies relating the receptor Fc&#947;RIIA to the leishmaniasis in humans. This way, this work consists in analyzing the allelic polymorphism in the gene that encodes the Fc&#61543;RIIA in individuals with American Tegumentary Leishmaniasis (ATL), evaluate if this polymorphism would be a genetic fact of susceptibility or resistance for this disease, if this would be influencing in the development of the different clinical forms of the ATL, as well in the healing process of the lesions. The Fc&#947;RIIA H/R131 polymorphism was analyzed in 88 blood samples of individuals with leishmaniasis and in 98 samples of healthy individuals (control group), using PCR, amplifying a segment of the gene that encodes the Fc&#61543;RIIA, followed by allele-specific enzymatic digestion and agarose gel eletrophoresis 3%. These results showed that the genotypic and allelic distribution of the Fc&#947;RIIA H/R131 were similar in the patients with leishmaniasis and in the control group, as well in patients with different clinical forms of the ATL. Concerning the resolution time of the disease, among the patients that had their lesions healed within one month of treatment or after this period, there was a predominance of the alleles R and H, respectively, however these differences were not significant. This way, our study suggests that the allelic polymorphism of the Fc&#947;RIIA H/R131 possibly is not a genetic factor of host that is associated to the protection or pathogenesis in the American Tegumentary Leishmaniasis. / O FcyRIIA, receptor para região Fc de IgG, expresso por macrófagos, neutrófilos, plaquetas e células dendríticas, liga-se às subclasses de anticorpos IgG com afinidade variável, que pode ser influenciada pelo polimorfismo alélico no gene que codifica este receptor. A troca do aminoácido arginina (R) para histidina (H) na posição 131 determina três padrões alélicos: os homozigotos H/H e R/R e o heterozigoto H/R, conferindo ao Fc&#947;RIIA H/H131 maior afinidade para as subclasses IgG2 e IgG3. Isto pode resultar em diferentes respostas frente a patógenos diversos. Alguns estudos demonstram a importância dos receptores Fc&#947; na infecção de macrófagos por formas amastigotas de Leishmania sp, em adição aos receptores para complemento (CR3) e para manose (MR). Além disso, vários fatores genéticos do indivíduo estão envolvidos na resposta imune à leishmaniose, dentre esses os FcyRs. Até o presente momento, não encontramos estudos relacionando o receptor Fc&#947;RIIA com a leishmaniose em humanos. Assim, o presente trabalho teve como objetivo analisar o polimorfismo alélico no gene que codifica o receptor FcyRIIA em indivíduos com Leishmaniose Tegumentar Americana (LTA), avaliar se este polimorfismo seria um fator genético de susceptibilidade ou resistência para esta doença, se estaria influenciando no desenvolvimento das diferentes formas clínicas da LTA, bem como no tempo de cura das lesões. O polimorfismo do Fc&#947;RIIA H/R131 foi analisado em 88 amostras sangüíneas de indivíduos com LTA e em 98 amostras de indivíduos saudáveis (grupo controle), através da PCR, amplificando um segmento do gene que codifica o Fc&#947;RIIA, seguida de digestão enzimática alelo-específica e eletroforese em gel de agarose 3%. Nossos resultados demonstraram que a distribuição genotípica e alélica do Fc&#947;RIIA - H/R131 foi similar nos pacientes com leishmaniose e no grupo controle, bem como nos pacientes com as diferentes formas clínicas da LTA. Em relação ao tempo de resolução da doença, nos pacientes que tiveram suas lesões curadas com até um mês de tratamento ou após esse período, houve um predomínio do alelo R e do H, respectivamente, entretanto essas diferenças não foram significativas. Assim, nosso estudo sugere que o polimorfismo alélico do Fc&#947;RIIA H/R131 possivelmente não é um fator genético do hospedeiro que esteja associado com proteção ou patogênese na Leishmaniose Tegumentar Americana.
194

The Neural Underpinnings of Worry: Investigating the Neural Activity and Connectivity in Excessive Worriers

Weber-Göricke, Fanny 01 December 2021 (has links)
Hintergrund. Exzessives Sorgen ist durch anhaltende, sich wiederholende negative Gedanken gekennzeichnet, die als aufdringlich und unkontrollierbar empfunden werden. Chronisches Sorgen kann zu einer schwer beeinträchtigenden mentalen Aktivität werden und es wird angenommen, dass es zur Entstehung, Aufrechterhaltung und Verschlechterung einer Reihe von somatischen Gesundheitsproblemen und psychischen Störungen beiträgt. Theoretische Modelle und empirische Befunde deuten darauf hin, dass exzessives Sorgen mit einer gestörten Bottom-up-Salienzverarbeitung, einer unzureichenden Top-down-Aufmerksamkeitssteuerung, Defiziten in der Emotionsregulation und abnormalen selbstreferenziellen mentalen Funktionen verbunden sind. Neuroimaging-Studien zu exzessivem Sorgen zeigen Veränderungen funktioneller Aktivierung und Konnektivität in limbischen und paralimbischen Hirnstrukturen, welche die Reaktivität auf emotionale Stimuli unterstützen, in präfrontalen Strukturen, die in Top-down-Prozesse involviert sind, welche der Aufmerksamkeitssteuerung und Emotionsregulation zugrunde liegen, und in medialen kortikalen Mittellinienstrukturen, die an selbstreferenziellen mentalen Aktivitäten beteiligt sind. Im Hinblick auf das Vorhandensein, die genaue Lokalisation der beteiligten Hirnareale und die Richtung der Effekte präsentieren diese Studien jedoch weitgehend heterogene Ergebnisse. Die hohe Variabilität der Befunde erschwert es, ein kohärentes Verständnis der neurobiologischen Mechanismen exzessiven Sorgens zu erlangen. Um dieses Verständnis zu erweitern und künftige Richtungen für die weitere Forschung auf diesem Gebiet aufzuzeigen, verfolgte die vorliegende Dissertationsschrift drei Ziele: (i) die emotionsbezogene, aufgabenbasierte fMRT-Literatur zu exzessivem Sorgen auf quantitative, datengesteuerte Weise zusammenzufassen, um konsistente funktionelle Störungen über Studien hinweg zu identifizieren; (ii) zu bestimmen, mit welchen psychologischen Prozessen die identifizierten Hirnregionen assoziiert sind, und in welchen funktionellen Hirnnetzwerken sie wirken; und (iii) Anomalien in der grundlegenden Hirnorganisation zu untersuchen, die mit exzessivem Sorgen assoziiert sind. Methoden. Eine State-of-the-Art koordinatenbasierte Meta-Analyse wurde unter Anwendung des Activation Likelihood Estimation (ALE) Algorithmus durchgeführt, um die Übereinstimmung zwischen 16 Neuroimaging-Experimenten zu bestimmen, die Veränderungen in der funktionellen Aktivität des Gehirns während der Verarbeitung emotionaler Inhalte zwischen Personen mit hoher und normaler Sorgenneigung berichten. Die identifizierten Regionen wurden mithilfe von Metadaten der funktionellen Magnetresonanztomographie (fMRT) hinsichtlich ihrer psychologischen Funktionen charakterisiert (Verhaltens-Charakterisierung). Zusätzlich wurde meta-analytic-connectivity modeling (MACM) verwendet, um ihre globalen funktionellen Konnektivitätsmuster zu bestimmen und so zugehörige Gehirnnetzwerke zu identifizieren. Schließlich wurde fMRT im Ruhezustand (resting-state) verwendet, um die funktionellen Konnektivitätsmuster zwischen 21 Personen mit hoher und 21 Personen mit normaler Sorgenneigung ohne einer aufgabenbezogenen Gehirnaktivierung zu vergleichen. Dispositionelle Sorgen wurden mit dem Penn State Worry Questionnaire als verlässliches Selbstauskunftsmaß für schwere Sorgen erhoben. Saatregion-basierte Analysen mit den meta-analytisch abgeleiteten Hirnregionen als Saatregionen und eine datengesteuerte Multi-Voxel-Pattern-Analyse (MVPA) wurden durchgeführt, um funktionelle Konnektivitätsunterschiede zwischen den beiden Gruppen zu detektieren. Darüber hinaus wurden gruppenüber-greifende Korrelationen zwischen dem aktuellen Sorgenausmaß (State-Sorgen) und den funktionellen Konnektivitätsmustern der Saat-Regionen sowie den aus der MVPA abgeleiteten Komponenten-Werten analysiert. Ergebnisse. Die Meta-Analyse ergab konvergente Anomalien bei Individuen mit hoher im Vergleich mit normaler Sorgenneigung, hauptsächlich in einem linkshemisphärischen Cluster, welcher Teile des mittleren frontalen Gyrus, des inferioren frontalen Gyrus und der anterioren Insula umfasst. Die Verhaltens-Charakterisierung zeigte, dass der identifizierte Cluster mit der Sprachverarbeitung und dem Gedächtnis assoziiert ist. Darüber hinaus ergaben die meta-analytischen Konnektivitätskartierungen starke funktionelle Verbindungen zwischen den beobachteten konvergenten Regionen und frontalen, temporalen und parietalen Hirnregionen, die sich mit Teilen von zwei verhaltensrelevanten Hirnnetzwerken überschneiden, nämlich dem Salienznetzwerk (SN) und dem Default-Netzwerk (DN). Die resting-state funktionellen Konnektivitätsanalysen zeigten keine Unterschiede zwischen Individuen mit hoher und normaler Sorgenneigung und auch keine Korrelationen zwischen den resting-state funktionellen Konnektivitätsmustern und State-Sorgen, weder mit dem auf Saatregionen basierenden Ansatz noch mit dem MVPA-Ansatz. Schlussfolgerungen. Die Ergebnisse dieser Dissertationsschrift deuten darauf hin, dass exzessives Sorgen mit einer gestörten Funktion in Hirnarealen zusammenhängt, die mit bottom-up und top-down Aufmerksamkeitssteuerung sowie Emotionserzeugung und Emotionsregulation in Verbindung gebracht werden. Die Verhaltensanalyse deckte Assoziationen zwischen dem identifizierten Cluster und der Sprachverarbeitung auf, die mit dem übermäßigen inneren Sprechen bei zu Sorgen neigenden Personen zusammenhängen könnten. Diese Assoziation ist bisher eher unbeachtet geblieben und sollte weiter erforscht werden. Darüber hinaus stellen die identifizierten Hirnregionen Schlüsselknoten in interagierenden neuronalen Netzwerken dar, die endogen und exogen orientierte Kognition unterstützen und das dynamische Zusammenspiel zwischen diesen Prozessen steuern. Ihre veränderte netzwerkübergreifende Dynamik könnte die Ursache für die Unfähigkeit von zu schweren Sorgen neigen-den Personen sein, sich von intern orientierten Kognitionen zu lösen, wenn adaptives Reagieren einen externen Fokus der Aufmerksamkeit erfordern würde. Die Nullergebnisse der Ruhezustandsanalysen könnten auf das Studiendesign zurückzuführen sein oder durch Charakteristika des Sorgens selbst verursacht werden, werden aber nicht als Beleg dafür interpretiert, dass Anomalien in der intrinsischen Konnektivität des Gehirns in Verbindung mit exzessivem Sorgen nicht vorhanden sind. Die Ergebnisse dieser Arbeit können zukünftige Forschungen anleiten, die z.B. untersuchen könnten, ob und wie sich die dynamischen zeitlichen Interaktionen innerhalb und zwischen den hier identifizierten Netzwerken in Abhängigkeit vom Schweregrad des Sorgens unterscheiden. Die ALE-Ergebnisse liefern eine A-priori-Auswahl von Hirnregionen für solche Studien. Ein besseres Verständnis der Veränderungen in den Gehirnnetzwerken, die exzessivem Sorgen zugrunde liegen, und der psychologischen Funktionen, die dadurch beeinträchtigt werden, wird Ansatzpunkte für die Verbesserung therapeutischer Interventionen liefern.:Contents TABLES VIII FIGURES IX ABBREVIATIONS X ABSTRACT 1 1 THEORETICAL BACKGROUND 6 1.1 WORRY 6 1.1.1 DEFINITION, NATURE AND FUNCTION OF WORRY 6 1.1.2 THE WORRY CONTINUUM – NORMAL VERSUS MALADAPTIVE WORRY 7 1.1.3 THE DELETERIOUS EFFECTS OF EXCESSIVE WORRY 8 1.1.4 THEORETICAL MODELS OF EXCESSIVE WORRY 11 1.2 FUNCTIONAL BRAIN NETWORKS AND EXCESSIVE WORRY 18 1.2.1 A SYSTEMS NEUROSCIENCE VIEW OF EXCESSIVE WORRY 18 1.2.2 EMPIRICAL EVIDENCE: FMRI STUDIES ON EXCESSIVE WORRY 20 1.3 RESEARCH QUESTION 32 2 STUDY I: A QUANTITATIVE META-ANALYSIS OF FMRI STUDIES INVESTIGATING EMOTIONAL PROCESSING IN EXCESSIVE WORRIERS: APPLICATION OF ACTIVATION LIKELIHOOD ESTIMATION ANALYSIS 35 2.1 ABSTRACT 36 2.2 INTRODUCTION 37 2.3 METHODS 40 2.3.1 LITERATURE SEARCH AND STUDY SELECTION 40 2.3.2 ACTIVATION LIKELIHOOD ESTIMATION 46 2.3.3 META-ANALYTIC CONNECTIVITY MODELING 47 2.3.4 ANALYSIS OF BEHAVIORAL DOMAIN PROFILES 47 2.4 RESULTS 48 2.4.1 SIGNIFICANT ALE CLUSTERS 48 2.4.2 FUNCTIONAL CONNECTIVITY OF THE DERIVED ALE-CLUSTER – MACM-ANALYSIS 51 2.4.3 FUNCTIONAL CHARACTERIZATION OF THE DERIVED ALE-CLUSTER – BEHAVIORAL ANALYSIS 54 2.5 DISCUSSION 55 2.6 CONCLUSION 59 2.7 SUPPLEMENTARY MATERIAL STUDY I: LISTING OF ALE CLUSTERS SIGNIFICANT AT P < 0.001 UNCORRECTED, CLUSTER SIZE > 100MM3 60 3 STUDY II: HIGH AND LOW WORRIERS DO NOT DIFFER IN UNSTIMULATED RESTING-STATE BRAIN CONNECTIVITY 61 3.1 ABSTRACT 62 3.2 INTRODUCTION 63 3.3 MATERIALS AND METHODS 65 3.3.1 PARTICIPANTS AND PROCEDURE 65 3.3.2 FMRI DATA ACQUISITION 66 3.3.3 SELF-REPORT ASSESSMENTS AND STATE WORRY ASSESSMENT 66 3.3.4 STATISTICAL ANALYSES 67 3.4 RESULTS 69 3.4.1 SELF-REPORT MEASURES 69 3.4.2 FMRI RESULTS 72 3.5 DISCUSSION 72 3.6 CONCLUSION 75 3.7 SUPPLEMENTARY MATERIAL STUDY II: STATE WORRY ASSESSMENT 75 4 GENERAL DISCUSSION 76 4.1 CONVERGENT ABERRANT FUNCTION IN THE MFG-IFG-INSULA-CLUSTER 76 4.2 META-ANALYTIC FUNCTIONAL CHARACTERIZATION AND CONNECTIVITY MAPPING OF THE MFG-IFG-INSULA CLUSTER 82 4.3 NO RESTING-STATE FUNCTIONAL CONNECTIVITY DIFFERENCES BETWEEN HW AND LW 84 4.4 STRENGTHS AND LIMITATIONS 87 4.5 FUTURE DIRECTIONS 90 4.6 CONCLUSION 91 REFERENCES 92 APPENDIX: DECLARATION OF HONOUR / EIGENSTÄNDIGKEITSERKLÄRUNG 131 / Background. Excessive worry is characterized by persistent, repetitive negative thoughts that are perceived as intrusive and uncontrollable. Chronic worrying can become a severely debilitating mental activity and is thought to contribute to the development, maintenance and deterioration of a range of somatic health problems and mental disorders. Theoretical accounts and empirical findings suggest that excessive worry is associated with impaired bottom-up salience-processing, insufficient top-down attentional control, deficits in emotion regulation and abnormal self-referential mental functions. Neuroimaging studies of excessive worry indicate functional activation and connectivity alterations in limbic and paralimbic brain structures that support reactivity to emotional stimuli, in prefrontal structures implicated in top-down processes underlying attentional control and emotion regulation, and in cortical midline structures involved in self-referential mental activity. However, with regard to the presence, the exact localization of the brain areas involved and the directionality of the effects, these studies have presented largely heterogenous results. The high variability of findings makes it difficult to achieve a coherent understanding of the neurobiological mechanisms of excessive worry. To extend this understanding and provide future directions for continued research in this area, the aim of this thesis was threefold: (i) to synthesize the emotional task-based fMRI literature on excessive worry in a quantitative, data-driven manner for the purpose of identifying consistent functional perturbations across studies; (ii) to determine the psychological processes with which the identified brain regions are associated and the functional brain networks in which they operate; and (iii) to examine abnormalities in basic brain organization associated with excessive worry. Methods. A state-of-the-art coordinate-based meta-analysis was conducted applying the activation likelihood estimation (ALE) algorithm to determine concordance among 16 neuroimaging experiments reporting alterations in brain functional activity during emotional processing between individuals experiencing high versus normal levels of worry. The identified regions were behaviorally characterized using functional magnetic resonance imaging (fMRI) metadata. Additionally, meta-analytic-connectivity modeling (MACM) was used to determine their global functional connectivity (FC) patterns and thus identify related brain networks. Finally, resting-state fMRI was used to compare FC patterns between 21 high and 21 low worriers in the absence of task-related brain activation. Dispositional worry was assessed using the Penn State Worry Questionnaire as a reliable self-report measure of severe worry. Seed-based analyses with the meta-analytically derived brain regions as seeds and a data-driven multi-voxel pattern analysis (MVPA) were performed to detect FC differences between the two groups. In addition, cross-group correlations between state worry levels and the FC patterns of the seed regions as well as the MVPA-derived component scores were analyzed. Results. The meta-analysis revealed convergent aberrations in high compared to normal worriers mainly in a left-hemispheric cluster comprising parts of the middle frontal gyrus, inferior frontal gyrus and anterior insula. Behavioral characterization indicated the identified cluster to be associated with language processing and memory. Furthermore, meta-analytic connectivity mapping yielded strong functional connections between the observed convergent regions and frontal, temporal, and parietal brain regions that overlap with parts of two behaviorally relevant brain networks, specifically the salience network (SN) and the default network (DN). The resting-state FC (rsFC) analyses revealed no differences between high and normal worriers and also no correlations between rsFC patterns and state worry, neither using the seed-based nor the MVPA approach. Conclusions. The results of this thesis indicate that excessive worry is related to disturbed functioning in brain areas that have been related to bottom-up and top-down attentional control as well as emotion generation and regulation. Behavioral analysis uncovered associations between the identified cluster and language processing that might be related to the exaggerated inner speech processes in worry prone individuals. This association has so far remained rather unnoticed and requires further exploration. Moreover, the identified brain regions constitute key nodes within interacting neural networks that support internally and externally oriented cognition and control the dynamic interplay among these processes. Their altered cross-network dynamics may underlie the inability of worry-prone individuals to disengage from internally oriented cognitions when adaptive responding would require an external focus of attention. The null-findings of the resting-state analyses might be due to the study design or caused by characteristics of worry itself, but are not interpreted as evidence that abnormalities in the brain's intrinsic connectivity associated with excessive worrying are absent. The results of this thesis may guide future research that could, for example, investigate whether and how the dynamic temporal interactions within and between the networks identified here differ depending on the severity of worry. The ALE results provide an a priori selection of brain regions for such studies. Increasing our understanding of the aberrations in brain networks that underlie excessive worry and the psychological functions that are impaired as a result will provide targets for improving therapeutic interventions.:Contents TABLES VIII FIGURES IX ABBREVIATIONS X ABSTRACT 1 1 THEORETICAL BACKGROUND 6 1.1 WORRY 6 1.1.1 DEFINITION, NATURE AND FUNCTION OF WORRY 6 1.1.2 THE WORRY CONTINUUM – NORMAL VERSUS MALADAPTIVE WORRY 7 1.1.3 THE DELETERIOUS EFFECTS OF EXCESSIVE WORRY 8 1.1.4 THEORETICAL MODELS OF EXCESSIVE WORRY 11 1.2 FUNCTIONAL BRAIN NETWORKS AND EXCESSIVE WORRY 18 1.2.1 A SYSTEMS NEUROSCIENCE VIEW OF EXCESSIVE WORRY 18 1.2.2 EMPIRICAL EVIDENCE: FMRI STUDIES ON EXCESSIVE WORRY 20 1.3 RESEARCH QUESTION 32 2 STUDY I: A QUANTITATIVE META-ANALYSIS OF FMRI STUDIES INVESTIGATING EMOTIONAL PROCESSING IN EXCESSIVE WORRIERS: APPLICATION OF ACTIVATION LIKELIHOOD ESTIMATION ANALYSIS 35 2.1 ABSTRACT 36 2.2 INTRODUCTION 37 2.3 METHODS 40 2.3.1 LITERATURE SEARCH AND STUDY SELECTION 40 2.3.2 ACTIVATION LIKELIHOOD ESTIMATION 46 2.3.3 META-ANALYTIC CONNECTIVITY MODELING 47 2.3.4 ANALYSIS OF BEHAVIORAL DOMAIN PROFILES 47 2.4 RESULTS 48 2.4.1 SIGNIFICANT ALE CLUSTERS 48 2.4.2 FUNCTIONAL CONNECTIVITY OF THE DERIVED ALE-CLUSTER – MACM-ANALYSIS 51 2.4.3 FUNCTIONAL CHARACTERIZATION OF THE DERIVED ALE-CLUSTER – BEHAVIORAL ANALYSIS 54 2.5 DISCUSSION 55 2.6 CONCLUSION 59 2.7 SUPPLEMENTARY MATERIAL STUDY I: LISTING OF ALE CLUSTERS SIGNIFICANT AT P < 0.001 UNCORRECTED, CLUSTER SIZE > 100MM3 60 3 STUDY II: HIGH AND LOW WORRIERS DO NOT DIFFER IN UNSTIMULATED RESTING-STATE BRAIN CONNECTIVITY 61 3.1 ABSTRACT 62 3.2 INTRODUCTION 63 3.3 MATERIALS AND METHODS 65 3.3.1 PARTICIPANTS AND PROCEDURE 65 3.3.2 FMRI DATA ACQUISITION 66 3.3.3 SELF-REPORT ASSESSMENTS AND STATE WORRY ASSESSMENT 66 3.3.4 STATISTICAL ANALYSES 67 3.4 RESULTS 69 3.4.1 SELF-REPORT MEASURES 69 3.4.2 FMRI RESULTS 72 3.5 DISCUSSION 72 3.6 CONCLUSION 75 3.7 SUPPLEMENTARY MATERIAL STUDY II: STATE WORRY ASSESSMENT 75 4 GENERAL DISCUSSION 76 4.1 CONVERGENT ABERRANT FUNCTION IN THE MFG-IFG-INSULA-CLUSTER 76 4.2 META-ANALYTIC FUNCTIONAL CHARACTERIZATION AND CONNECTIVITY MAPPING OF THE MFG-IFG-INSULA CLUSTER 82 4.3 NO RESTING-STATE FUNCTIONAL CONNECTIVITY DIFFERENCES BETWEEN HW AND LW 84 4.4 STRENGTHS AND LIMITATIONS 87 4.5 FUTURE DIRECTIONS 90 4.6 CONCLUSION 91 REFERENCES 92 APPENDIX: DECLARATION OF HONOUR / EIGENSTÄNDIGKEITSERKLÄRUNG 131
195

Návrh a realizace systému zpracování dat z environmentálních čidel v prostředí IoT / Design and realization of data processing system from environmental sensors in IoT environment

Maraczek, Patrik January 2020 (has links)
The master’s thesis deal with design and realization of measuring station, which process data from environmental sensors in IoT environment. Thesis includes research of sensors, cloud services for IoT, microcontrollers and environmental data available online. Thesis contains detailed procedure for realization of designed system, including code description for microcontrollers STM32W55 and STM32 B-L475E-IOT01A2 Discovery kit, configuration of IBM Watson IoT Platform cloud service and procedure for correct programming of Node-RED application responsible for logic of whole system. Source code, which might be used for simple implementation of designed system, is attached to the master’s thesis.
196

LCC MSE Walls

Smith, Joel 08 December 2023 (has links) (PDF)
Lightweight cellular concrete (LCC) is mainly a mixture of water, cement, and foam bubbles. LCC generally has a cast density between 20-60 pcf and an air content between 49-84%. LCC is often used as a fill material because it has a low unit weight which reduces settlement. LCC is increasingly being considered as a backfill behind Mechanically Stabilized Earth (MSE) walls and embankments. Although engineers are using LCC in MSE walls or free face walls (MSE wall without the concrete panels or reinforcements), there is presently a lack of information regarding the performance and behavior of LCC to guide them. This research attempts to answer questions on the design of MSE walls backfilled with LCC and free face LCC walls by providing a well-documented case history and evaluating if LCC can be modeled as a c-ϕ material. A steel frame test box (10 ft wide x 12 ft long x 10 ft high) with a MSE wall on one side was constructed for the research. The box was filled with four lifts of LCC with steel ribbed-strip reinforcements extending into the LCC behind the MSE wall panels at the center of each lift. After the LCC was cured, two static load tests were performed by applying a surcharge load to the surface of the LCC. In one test, surcharge pressure was applied adjacent to the MSE wall to produce failure of the wall system. In a second test, the surcharge pressure was placed adjacent to a free face of the LCC to produce failure. String potentiometers (string pots), load cells, pressure plates, and strain gages were used to measure the behavior of the MSE wall and free face wall during testing. These two tests provided a comparison between LCC behavior with a MSE wall relative to a LCC free face. Failure of the free face wall with unreinforced LCC backfill in this test can be predicted using Rankine’s lateral force equation using a c-ϕ model. Failure angle at the base of the free face wall was between 51-63° which corresponds with an average friction angle (ϕ) of 24° and cohesion (c) of 1575 psf with an upper bound ϕ = 34° and a c = 1285 psf. The presence of reinforcements in the LCC backfill behind the MSE wall increased the capacity of the wall to hold a surcharge load. The presence of reinforcements in the LCC behind MSE walls also led to a much more ductile surcharge pressure vs. lateral deflection curve for the MSE wall compared to the free face wall.
197

Gender agreement in Native and Heritage Greek: an attraction study

Paspali, Anastasia 29 November 2019 (has links)
Diese Dissertation betrachtet die Beziehung zwischen Parser und Grammatik bei Muttersprachlern (Native Speakers, NS) und Heritage- (Erb-) Sprechern (HS) des Griechischen, indem sie die Mechanismen untersucht, die einer pseudo-Lizenzierung bei Verletzungen der Kongruenz des grammatischen Geschlechts zugrunde liegen. Diese Verletzungen sind Fehler, die auftreten, wenn eine intervenierende Phrase (Attraktor) nicht mit den Genusmerkmalen des Kopfnomens übereinstimmt, ein Phänomen, das in der Literatur (Gender-)Agreement Attraktion, hier Attraktion von Genuskongruenz, genannt wird. Die Dissertation testet, ob eine solche Attraktion von Genuskongruenz im Griechischen vorhanden ist und ob ein- und zweisprachige Muttersprachler gleichermaßen anfällig für Fehler bei der Attraktion sind. Die Dissertation untersucht für die Gruppe der HS außerdem die Genuskongruenz beim Echtzeit-Sprachverstehen und -produzieren. In der Arbeit zeige ich, dass sowohl NS als auch HS anfällig für Attraktionsfehler bei der Genuskongruenz sind. Das zeigen die Reaktionszeitmuster und die Urteile. Gleichzeitig zeigten bei mündlichen Erzählungen beide Sprechergruppen die gleichen Übergeneralisierungsmuster für maskulines Genus bei belebten Nomen sowie bei mündlichen Erzählungen und beschleunigten Grammatikalitätsurteilen für Neutrum bei unbelebten Nomen. Zusammengenommen deuten diese Ergebnisse darauf hin, dass NS und HS anfällig für die Attraktion von Genuskongruenz sind und dass beide Gruppen ähnliche Hinweise zum Abruf des Genus verwenden und somit ähnliche Attraktionsmuster aufweisen. HS unterscheiden sich jedoch von NS in der Verarbeitung der Genuskongruenz an sich, insbesondere bei femininen Kopfnomen (markiertes Genus) in Objekt-Klitika, was darauf hindeutet, dass sowohl Markiertheit als auch Kongruenz an den Schnittstellen die Leistung von HS beeinflusst. Wenn Fehler auftreten, folgen beide Gruppen den gleichen Mustern der Übergeneralisierung. / This dissertation explores the relationship between the parser and the grammar in Native Speakers (NSs) and Heritage Speakers (HSs) of Greek by examining the mechanisms underpinning the illusory licensing of gender agreement violations: errors occurring when an intervening phrase (attractor) mismatches the gender cues of the head noun, a phenomenon which is usually called (gender) agreement attraction. In this work, I show that both NSs and HSs are prone to gender agreement attraction errors in the nominal domain of Greek, as their reaction time patterns and (speeded or scaled) judgements revealed. At the same time, both groups showed the same overgeneralization patterns of the masculine value in agreement errors with animate nouns in their oral narrations, and of the neuter value with inanimate nouns in their oral narrations and their online speeded judgements. Taken together, these results suggest that NSs and HSs are prone to gender agreement attraction in Greek and that both groups employ retrieval cues similarly showing similar attraction patterns. However, HSs differ from NSs in the processing of gender agreement per se, particularly with feminine head nouns (marked gender value) on object-clitics, suggesting that markedness as well as agreement at Interfaces influence HSs’ performance. Finally, when errors occur, both groups follow the same overegeneralization patterns.
198

Challenges of an SME in the market ramp-up of fuel cells in terms of quantity & quality

Wannemacher, Thomas 25 November 2019 (has links)
Brennstoffzellen stellen aufgrund ihrer Vielseitigkeit, ihres Wirkungsgrades und ihrer systembedingten Vorteile eine ausgezeichnete Lösung zur Erzeugung von elektrischer Energie bei Bedarf dar. Zahlreiche Projekte haben die prinzipielle Einsatzbereitschaft dieser Technologie für stationäre, maritime und mobile Anwendungen gezeigt. Der Markthochlauf steht jedoch derzeit vor einigen Hürden. Besonderes Augenmerk wird darauf gelegt, wie kleine und mittlere Unternehmen (KMU) diese überwinden können. Diese Hindernisse werden im Kontext der allgemeinen Marktsituation im Allgemeinen sowie in der Brennstoffzellenindustrie grundlegend analysiert. Möglichkeiten zur Kostensenkung bei steigenden Produktionsmengen und zur Sicherstellung der erforderlichen Produktqualität werden diskutiert. Die zu produzierenden Stückzahlen sind je nach Marktsegment sehr unterschiedlich. Daher ist es unerlässlich, dass die Produktionskapazitäten mit der tatsächlichen Nachfrage nach Brennstoffzellensystemen und -produkten wachsen. Ein universelles Brennstoffzellensystem, das nur einfache Anpassungen für verschiedene Anwendungen erfordert, kann hier eine Lösung sein. / Fuel cells represent an excellent solution for generating electrical power on demand because of their versatility, efficiency and system-related advantages. Numerous projects have shown the readiness of this technology for stationary, maritime and mobile applications. However the market ramp-up presently faces certain hurdles. Particular attention is paid to how small and medium sized enterprises (SMEs) can overcome them. These obstacles are put in context by an analysis of the general market Situation within the fuel cell industry. Opportunities for the reduction of costs as production quantities ramp up whilst assuring the necessary product quality are discussed. The quantities involved are vary between individual market segments. Therefore it is imperative that production capacities grow in line with the actual demand for fuel cell systems and products. A universal fuel ce/1 system design which only needs simple adaptations for different applications can be a solution here.
199

Durch Lumineszenz nachgewiesene magnetische Resonanz: Aufbau eines Spektrometers und Messungen an den Laserkristallen Al2O3:Cr und Al2O3:Ti / Magnetic resonance detected via luminescence: construction of a spectrometer and measurements of the laser crystals Al2O3:Cr and Al2O3:Ti

Ruza, Egils 15 September 2000 (has links)
Im Rahmen dieser Arbeit wurde eine Meßanordnung zum Nachweis der Elektronen-Spin-Resonanz durch Beobachtung der Lumineszenz aufgebaut. Diese Methode ist unter dem Namen Optisch Detektierte Magnetische Resonanz (ODMR) bekannt. Sie erlaubt es, die Lumineszenzeigenschaften mit der aus der Spin-Resonanz gewonnenen atomistischen Strukturinformation zu verknüpfen. Mit der ODMR-Anlage wurden Untersuchungen an zwei unterschiedlich dotierten Korund-Kristallen, Rubin (Al2O3:Cr) und Saphir (Al2O3:Ti), durchgeführt. Anhand der Literaturdaten für Rubin wurde die neu aufgebaute Anlage getestet und geeicht. Die Messungen an Saphir dienten zur Klärung der bisher kontrovers diskutierten Struktur von blau emittierenden Lumineszenzzentren. Bei einer UV-Anregung entsteht im Saphir neben der schon bekannteninfraroten Ti3+-Emission eine breite blau-grüne Emission, die aus zwei überlappenden Teilbanden besteht. Die eine hat das Maximum bei ca. 410 nm ("blaue Bande") und die andere bei 480 nm ("grüne Bande"). Die Anregung beider Lumineszenzbanden findet bei 250 nm und 270 nm bzw. 270 nm statt. Um diese blau-grüne Lumineszenz zu erklären, sind unterschiedliche Modelle vorgeschlagen worden. So wurde die Lumineszenz F+-Zentren (ein Elektron in einer Sauerstoffleerstelle) oder Ti-Zentren zugeordnet. Im Falle der Ti-Zentren wurden alternativ Kristallfeldübergänge von Ti3+-Ionen und Charge-Transfer-Übergänge von Ti4+-Ionen mit der Lumineszenz in Verbindung gebracht. Die im Rahmen dieser Arbeit durchgeführten ODMR-Messungenergaben als Ursache der blau-grünen Lumineszenz zwei einander ähnliche Triplett-Systeme T1 und T2. Diese konnten durch folgende ESR-Parameter beschrieben werden: T1: gx,y,z=2.00, 1.96, 1.94 (g-Tensor), D=0.306 cm-1 (axialer Anteil der Kristallfeldaufspaltung), E=0.034 cm-1 (orthorhombischer Anteil der Kristallfeldaufspaltung); T2: gx,y,z=1.99, 1.99, 1.99, D=0.342 cm-1, E=0.054 cm-1. Das Zentrum T1 konnte der blauen und T2 der grünen Lumineszenz-Teilbande zugeordnet werden. Da die Lumineszenz-Zentren angeregte Tripletts sind, können Dublett-Systeme wie die F+-Zentren oder Ti3+-Ionenausgeschlossen werden. Dagegen sind die Beobachtungen verträglich mit dem Ti4+-O2--Charge-Transfer-Modell (mit Ti3+-O- im angeregten Zustand). Beide Lumineszenzbanden stammen demzufolge aus der Rekombination des Elektron-Loch-Paares im Ti3+-O--Zentrum des Typs T1 oder T2, das durch den Charge-Transfer-Übergang eines Elektrons vom Sauerstoff zum Ti4+ entsteht. Elektron und Loch koppeln zu einem Triplett-System. Das Loch ist bei beiden Zentren an einem dem Titanion benachbarten Sauerstoffion lokalisiert. Dies wird daraus geschlossen, daß die z-Achse der ESR-Tensoren ungefähr parallel zur Richtung der Al-O-Bindungen im ungestörten Kristallgitter liegt. Für beide Zentren ist das Verhältnis aus axialem undorthorhombischem Kristallfeldparameter |D/E| ungefähr gleich. Dies läßt auf eine ähnliche Struktur der Umgebung schließen, was das Bild unterstützt, daß beide Zentren fast identisch aufgebaut sind. Der axiale Kristallfeldanteil (Parameter D) von T2 ist etwas größer als der von T1. Dies kann durch einen kleineren Abstand von Elektron und Loch, d. h. von Ti3+ und O- erklärt werden, da die Kopplung zwischen den Spins dann stärker sein wird. In ungestörtem Al2O3 weisen drei der sechs einem Al-Ion benachbarten Sauerstoffionen einen kleineren Abstand auf als die anderen drei Ionen. Die drei Sauerstoffionen mit gleichem Abstand bilden jeweils Dreiecke, wobei das mit dem kleineren Abstand eine größere Seitenlänge aufweist. Es besteht nun die Möglichkeit, daß die beiden Zentren T1 und T2 sich lediglich darin unterscheiden, daß das Loch einmal auf einem Ion des kleinen und einmal auf einem des großen Dreiecks eingefangen ist. Wegen der Größe von D wäre T1 dann dem kleinen und T2 dem großen Dreieck zuzuordnen. Auch die beobachteten Hauptachsenrichtungen der ESR-Tensoren sind mit dieser Zuordnung verträglich. Im angeregten Zustand befindet sich das Elektron auf dem Titanion imgleichen Zustand wie das in dem Grundzustand des Ti3+-Ions. Der große Unterschied zwischen den in der ESR des Grundzustands gemessenen g-Werten (gparallel=1.067, gperp<0.1, Kask et al., 1964) und dem hier gewonnenen fast isotropen g-Faktor (g=2) kann durch die sogenannte Auslöschung des Bahndrehimpulses erklärt werden, die bei niedrigsymmetrischem System wie Ti3+-O- auftritt.
200

The Ugly Side of the Beautiful Game - Hooliganism in French Football

Amado, Carlos Josue 11 November 2008 (has links) (PDF)
Football violence was a rare phenomenon in France until the nineteen eighties. Harsh economic times coupled with the challenges of unemployment brought a different type of fanatic to football stadia. To vent their frustration about the economic difficulties of their time, some fans found an easy scapegoat: the increasing number of African immigrants in France. These fans, known as hooligans, have become organized and can be found supporting most major French football clubs, disrupting what once was a relatively tranquil national pastime. This thesis traces their development in France, looks at what they borrowed from Italian and English fan groups, and suggests how their organization is now uniquely French.

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